An infrared radiation detecting device is constructed using a manufacturing method to increase the infrared radiation absorptance of the infrared radiation absorbing film. Experimental thermal imaging data is acquired. Specifically, the selection of the number of molecules of the above electric discharge gas being about ten times that of the above-mentioned remaining gas or more can reduce the adverse effect by the above-mentioned remaining gas. In a second, disjoint corner features or other features are classified and similar features compared.